Piston



,1938. A. 1.. NELSON 2,128,662

PISTON Original Filed June 8, 1925 2 Sheets-Sheet 1 A. NELSON Aug. 30,1938.

PISTON 5 2 Sheets-Sheet 2 Original Filed June 8, 192

Shun-1 ml, Ado/phLNelson Patented Aug. 30, 1938 UNITED STATES PATENTOFFICE PISTON Mich.

Application June 8, 1925, Serial No. 35,703 Renewed May 6, 1938 2Claims.

My invention relates to a piston and it is an object of the same to makea piston of metal with suitable thermal qualities as, for instance,aluminum alloy and at the same time to control or decrease the expansionof the skirt to practically that of the.well-known cast-iron pistons.While I propose to decrease or control the expansion of the entireskirt, it is particularly important to decrease the expansion in apositive way at the upper portion of the skirt, which portion must be ofsufliciently rigid construction to sustain the thrust load of theconnecting rod. Experience in the use of the ordinary aluminum pistonsshows that if aluminum forms the material of the webs which join theskirt to the bosses, particularly the portions nearest the head, theexpansion of this metal will cause unduly high pressure between thecylinder and that part of the piston which may be designated as theshoulders i, e., the parts between the piston pin bosses and the headopposite thewebs,whichparts are directly subjected to the thrust of theexpansion of the webs and of the connecting rod.

According to my construction these webs are 25 omitted and are replacedwith struts of suitably rigid relatively inexpansible metal cast inplace above the pin bosses, the ends of the struts being embedded in theupper part of the skirt and the middle part of each strut being embeddedin a pin boss.

The lower part of the skirt, not being subject to as high temperaturesas the upper part of the piston, I propose to support same directly fromthe lower part of the piston pin bosses by means of webs or flanges asmay be conveniently cast integrally with the skirt and bosses.

Referring to the accompanying drawings, which are made a part hereof andon which similar reference characters indicate similar parts,

Figure 1 is an elevation 01' my device, Figure 2, an elevation partly insection at right angles to Fig. .1, Figure 3, a central section at rightangles to Fig. 2,

Figure 4, a horizontal section of the piston.

Figure 5, a horizontal section of a modifiedform, f Figure 6, ahorizontal section of still another orm,

Figure 7, a vertical section of a piston of modified form, Figure 8, anelevation of the same partly broken away on a plane at right angles tothat of Fig. 7, and

Figure 9, a detail of the strut used in said modified form.

In the drawings reference character in indicates a piston head of anydesirable or conventional form this piston head having depending 6therefrom integral bosses ii providing bearings for receiving a pistonpin. These bosses are cast in one piece with the head and with the skirt1! which is separate from the bosses and from the head except at thelower end of each boss where the skirt and bosses are cast in one pieceor otherwise rigidly secured to each other as by a web indicated at l3.The connection between the head and the boss is strengthened by a radialouter flange l4 and a radial inner flange l5 which flanges in efiectform a post extending length:- wlse of the bearing in the boss directlyabove the axis of the bearing such post providing a strong supportextending from the upper end of the head to the boss. A similar flangel6 extends from the lower side of the boss to the lower part of theskirt and coacts with a rib I1 (Fig. 3)

c to strengthen the connection between the piston boss and the skirt.

To further strengthen the upper end of the skirt I provide a pair ofstruts l8 of material such as steel which is relatively inexpansible asA compared with the material of the remainder of the piston. The struts,as will be seen in Figure 4, may be curved at the ends to provideholding portions embedded in the edges of the upward projections of theskirt and each strut may also have a transverse ridge or otherinequality at H! in -its intermediate partwhich is buried in the pistonpin boss or a part rigid therewith to help in holding the bosses andtheir skirt sections in correct relative position.

It is of .less importance to positively control the expansion in thelower part of the skirt and I do not propose to do this by means ofstruts as this would complicate the construction unduly. This part ofthe skirt may be ground to an oval form to permit expansion of the metalbelow the pin bosses or other suitable methods may be used to providefor expansion as by means of slots l9 extending up from the lower end ofthe skirt. The temperature of the lower part of the skirt is lowcompared with other parts of the piston and therefore the pressure atthe bottom of the skirt is also relatively low. Where the slots are usedthey should extend about half-way up the skirt. In some instances noslots or reliefs at the bottom of the skirt are necessary as only asmall portion of the heat in the piston head can get to the skirt andthe clearance at the upper 5 end of the skirt can be made so close withmy construction that a more liberal clearance can be allowed at thelower end of the skirt in which case the skirt is machined to a taperedform without slots or reliefs. Whether the bottom of the skirt forms acomplete annulus or is interrupted by slots I9 the general form will bethat of an annulus with upward extensions separated by recesses which ashere shown are wider than the bosses and extend below the bosses thoughthese proportions are not essential.

In the construction shown in Figure the struts 20 are curved. With thisconstruction the struts will be flexed as the head expands carrying thebosses l l outward and will so be made to resist outward movement of theextensions 2| of the skirt thus rendering the expansion of the skirtvery small.

The construction shown in Figure 6" is similar to that in Figure 5except that the struts 22 are of angular form with a straight portionembedded in the pin bosses, and straight portions at an angle to thatfirst-named reaching from the pin bosses to the skirt sections 23. Theoperation is similar to that in Figure 5. p

The construction shown in Figures 7, 8,'and 9 illustrates a modified wayof attaching the lower part of the skirt to the lower part of the pistonpin bosses. Flange I3 is extended sidewise doing away with flange I1 andrib "5 of Figure '1. The construction also shows a modified strut l8partly enveloping the bosses. The strut form is easily modified to suitpistons of various proportions. To weaken the lower part of the skirtslot I9" is shown on one side of the skirt only, and extends almost tothe top edge of the skirt.

It will be obvious to those skilled in the art that various changes maybe made in my device without vdeparting from the spirit of the inventionand therefore I do not limit myself to what is shown in the drawings anddescribed in the specification but only as indicated in the appendedclaims.

Having thus fully described my said invention, what I claim as new anddesire to secureby Letters Patent, is:

1. A piston comprising a head, piers depending from the head andcarrying piston pin bosses, a skirt of light-weight material having arelatively high rate of thermal expansion comprising a lower ring-likepart and thrust faces extending upwardly from the ring-like part atopposite sides of the skirt, the upper ends of the thrust facesbeingseparated from the head by slots, the ring-like part extending withoutinterruption from one thrust face to the other below each pin boss, atie extending downwardly and radially from each pin boss to thering-like part, said ties being homogeneous with the pin bosses and withthe ring-like part, and struts of material having a lower rate ofthermal expansion than the skirt material, the struts extendingapproximately at right angles to the axis of the piston pin bosses andhaving their opposite ends buried in the thrust faces and their middleparts engaged by the material of the piers.

2. A piston comprising a head, piers depending from the head andcarrying piston pin bosses, a skirt of light-weight material having arelatively high rate of thermal expansion comprising a lower ring-likepart and thrust faces extending upwardly from the ring-like part atopposite sides of the skirt, the upper ends of the thrust faces beingseparated from the head by slots, the ring-like part extending withoutinterruption from one thrust face to the other below each pin boss, atie extending downwardly and radially from each pin boss to the ringlikepart, said ties being homogeneous with the pin bosses and with thering-like part, the, outer surface of the lower end of the skirt havingan oval shape with the minor axis of the oval parallel to the axis ofthe pin bosses, and struts of material having a lower rate of thermalexpan-- sion than the skirt material, the struts extending approximatelyat right angles to the axis of the piston pin bosses and having theiropposite ends buried in the thrust faces and their middle parts engagedby the material of the piers.

ADOLPH L. NELSON.

